Vacuum skin packaging laminate, package and process for using same

ABSTRACT

The present invention is directed to vacuum skin packaging laminates. The laminates include a first film, a second film, an adhesive bonding the first film to the second film, and an adhesive-free interfacial section between the first and second films. The laminate is adapted to provide substantially horizontal first film-surface above the product for displaying product markings and a thermoformable second film-surface for conforming to the shape of the product. The present invention also is directed to vacuum skin packages formed from such laminates, and methods of packaging a product.

This application is a divisional application of U.S. patent applicationSer. No. 12/018,261, filed Jan. 23, 2008 now U.S. Pat. No. 8,047,368,issued on Nov. 1, 2011, which is incorporated herein by reference in itsentirety.

TECHNICAL FIELD

This invention relates to the field of packaging. Particularly, thepresent invention relates to packaging laminates suitable for use invacuum skin packaging applications, packages constructed from suchlaminates and methods of packaging a product.

BACKGROUND OF THE INVENTION

Vacuuming skin packaging (VSP) process is well known in the art andvarious apparatus and processes have been described, for example, inU.S. Pat. Nos. 3,835,618; 3,950,919 and Re 30,009, all issued to Perdue.The vacuum skin packaging process is in one sense a type ofthermoforming process in which an article to be packaged serves as themold for the thermoform. An article may be placed on a support member,such as a rigid or semi-rigid card, tray or other bottom support member;the supported article is then passed to a chamber where a film can beeither heated and draped over the article, or drawn upwards against aheated dome and then, draped over the article. The movement of the filmmay be controlled by vacuum and/or air pressure; and in a vacuum skinpackaging arrangement, the interior of the container may be evacuatedbefore final sealing of the film to the support. Typically,thermoformable materials may be used as the draping film. Examples ofvacuum skin packaging trays, films and processes are disclosed in U.S.Pat. Nos. 4,611,456 to Gillio-tos et al.; 5,846,582 to Mayfield et al.;and 5,916,613 to Stockley Ill., which are hereby incorporated byreference herein.

Vacuum skin packaging applications may include packaging of perishableor non-perishable food products, such as, e.g., fresh red meat andsliced cheese, or frozen food products, such as frozen fish, poultry andthe like. Typically, the packaging material for oxygen-sensitive foodand non-food products require lower oxygen permeability compare to thatfor non-oxygen sensitive products. For example, U.S. Patent ApplicationPublication No. 2006/0269707 to Otacilio Berbert, the disclosure ofwhich is hereby incorporated herein by reference, describes severalmultilayer thermoformable films suitable for use in vacuum skinpackaging applications of perishable food products. The disclosuredemonstrates that VSP films can be modified to provide an oxygentransmission rate of from about 0-2.0 cm³/100 in²/24 hours at 0% R.H.and 23° C. These films include an oxygen barrier layer comprisingethylene/vinyl alcohol copolymer and a surface-treated sealing layercomprising polyethylene vinyl acetate copolymer.

Generally, labels and printed indicia are located on a package where itmay be viewed by the consumer. Typically, these markings are positionedon a relatively smooth, flat upper surface of the package which allowsthe consumer to read product information without having to handle thepackage. Indicia on vacuum skin packages become illegible when locatedon the upper surface of the packaging film formed to an irregularlyshaped product. For this reason, vacuum skin packaging often includes anover-packaging technique, e.g., the use of an overwrap film, apaperboard sleeve or a carton box, which covers the vacuum skin packageand provides a flat surface for printed information. However,over-packaging is an extra cost to the manufacturer, and labels andother printed information applied underneath the package are notattractive to consumers who are accustomed to viewing the product andproduct information together.

Thus, it is an object of the present invention to overcome the labelingdifficulties of the prior art.

It is also an object of the present invention to provide a flexiblepackaging laminate for vacuum skin packaging applications.

It is also an object of the present invention to provide a flexiblepackaging laminate which separates into two films when subjected to heatand differential air pressure thereby forming a substantially horizontalfirst film-surface above a product and a thermoformable secondfilm-surface enclosing the product.

It is yet another object of the present invention to provide a vacuumskin package.

It is yet another object of the present invention to provide a vacuumskin package which provides a substantially horizontal film-surfacedisposed above the product and a thermoformed film-surface surroundingthe exterior shape of the product.

It is yet still another object of the present invention to provide amethod of vacuum skin packaging a product using a single flexiblelaminate.

BRIEF SUMMARY OF THE INVENTION

These as well as other objects are achieved by providing a flexiblepackaging laminate comprising a first film, a second film and anadhesive which adheres the first film to the second film, and anadhesive-free interfacial section between the first and second films.The adhesive-free interfacial section includes an unbound portion of thefirst film and an unbound portion of the second film. The unboundportion of the first film includes at least one perforation, cut orscore-line, extending through the entire thickness of the first film,and the unbound portion of the second film which is free of aperforation, cut and score-line. The unbound portions of the first andsecond films are adapted to separate from each other such that unboundportion of the second film can be drawn towards a product and theunbound portion of the first film remains substantially undistortedduring a vacuum thermoforming process.

The objects of the invention are further achieved by providing a packagecomprising a product-support member having an elevated distal flange, aproduct being supported on the product-support member, and a singleflexible laminate having at least two opposing perimeter edges heatsealed to the distal flange. The flexible laminate comprises a firstfilm being adhesively joined to a second film, and an adhesive-freeinterfacial section between the first and second films, wherein theadhesive-free interfacial section includes an unbound portion of thefirst film and an unbound portion of the second film. The packagefurther includes a substantially horizontal film-surface comprising theunbound portion of the first film. The substantially horizontalfilm-surface is positioned above the product and parallel with a planedefined between at least two opposing edges of the distal flange. Thepackage still further includes a thermoformed film-surface conformed tothe exterior shape of the product which comprises the unbound portion ofthe second film.

The objects of the invention are yet further achieved by providing amethod for packaging a product. The method comprises the steps of: a)providing a product-support member having an elevated distal flange; b)positioning the product on the product-support member; c) providing asingle flexible laminate comprising a first film being adhesively joinedto a second film, and having an adhesive-free interfacial sectionbetween the first and second films, wherein the adhesive-freeinterfacial section comprises an unbound portion of the first film andan unbound portion of the second film; d) heating the laminate; e)evacuating the space between both the laminate and product-supportmember, and subsequently pressurizing the space between both thelaminate and product-support member to separate the unbound portion ofthe first film from the unbound portion of the second film; f)conforming the unbound portion of the second film around the exteriorshape of the product; and g) sealing at least two opposing perimeteredges of the laminate to the distal flange thereby providing asubstantially horizontal film-surface disposed above the product. Thesubstantially horizontal film-surface includes the unbound portion ofthe first film which is parallel with a plane defined between twoopposing edges of the distal flange. Those skilled in the art willrecognize that process steps of conforming the second layer to theexterior shape of the product and sealing the laminate to the flange mayby accomplished either simultaneously or sequentially. The method of thepresent invention may further include the steps of printing indicia on asurface of unbound portion of the first film and placing a printed labelon the unbound portion of the first film.

Embodiments of the present invention provide the advantage ofeliminating the need for two or more individual packaging webs forvacuum skin packages bearing product markings clearly visible to theconsumer by reducing the number of webs to a single laminate. Thepresent invention is particularly beneficial to the food packagingindustry for vacuum skin packaging of irregularly shaped food productssince only a single laminate is needed. The present invention may reducethe cost and complexity of the packaging process.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

A detailed description of preferred embodiments of the inventionfollows: with reference to the drawings, wherein:

FIG. 1 is a cross-sectional view of one embodiment of the laminate ofthe present invention.

FIG. 2 is a cross-sectional view of another embodiment of the laminateof the present invention.

FIG. 3 is a partial top view of one embodiment of the laminate of thepresent invention having a plurality of perforations in the unboundportion of the first film.

FIG. 4 is a partial top view of another embodiment of the laminate ofthe present invention having a plurality of cuts or score-lines in theunbound portion of the first film.

FIG. 5 is a partial top view of one embodiment of the laminate of thepresent invention having a plurality of continuous adhesive segmentsapplied to the second film.

FIG. 6 is a partial top view of another embodiment of the laminate ofthe present invention having a single continuous adhesive segmentapplied to the second film.

FIG. 7 is a partial top view of another embodiment of the laminate ofthe present invention having a plurality of intermittent adhesivesegments applied to the second film.

FIG. 8 is a view of another embodiment of the laminate of the presentinvention.

FIG. 9 is a cross-sectional view of one embodiment of a package inaccordance with the present invention.

FIG. 10 is a cross-sectional view of one embodiment of a package inaccordance with the present invention during a vacuum skin packagingprocess.

FIG. 11 is a cross-sectional view of the package illustrated in FIG. 10during a vacuum skin packaging process.

FIG. 12 is another cross-sectional view of the package illustrated inFIG. 10 during a vacuum skin packaging process.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the terms “lamination” and “laminate” refers to theprocess and resulting product made by bonding together two or more filmsor film layers together. Lamination can be accomplished by joininglayers together with adhesives, with heat and pressure, with spreadcoating and/or with extrusion coating. The term film is also inclusiveof coextruded multilayer films.

The term “thermoplastic” describes a material that softens when exposedto heat and which substantially returns to a non-softened condition whencooled to room temperature. In some embodiments of the presentinvention, the first layer or the second layer, and preferable, at leastthe second layer of the film, comprises a thermoplastic material.Alternatively, both the first and second layers of the film include athermoplastic material:

The term “polymers” includes, but is not limited to, homopolymers,copolymers, such as for example, block, graft, random and alternatingcopolymers, terpolymers, etc. and blends and modifications thereof.Furthermore, unless otherwise specifically limited, the term “polymer”shall include all possible configurational isomers of the material.These configurations include, but are not limited to isotactic,syndiotactic and atactic symmetries

The term “adhesive” refers to a layer or material placed on one or morelayers to promote the adhesion of that layer to another surface. Unlessotherwise indicated, an adhesive layer can have any suitable compositionthat provides a desired level of adhesion with the one or more surfacesin contact with the adhesive layer material. Adhesives have beengenerally described in Kirk-Othmer-Adhesives; pg. 445-466; Vol. 1; 1991,by Aldophus Pocius, the disclosure of which is incorporated herein.Preferably, the adhesive is any packaging adhesive which may fluidadhesives, solvent-based adhesives, and solvent-free adhesives. As usedherein, the phrase “fluid adhesive” refers to any substance, inorganicor organic, natural or synthetic, that tends to flow under pressureand/or heat at a rate sufficient of coat a layer in a commercialprocess. Suitable fluid adhesives may have a wide range of viscositiesat room temperature and may have a variety of forms, which include, butare not limited to, for example, solutions, dispersions, emulsions,pastes, mastics, and the like. Suitable organic adhesives may includenatural adhesives, i.e., for example, hide and bone glue, fish glue,rubber latex, terpene resins, and mucilages, and synthetic adhesives,which include, but are not limited to polyvinyl acetate emulsions,ethylene/vinyl acetate copolymers, polyurethanes, silicone polymers,cyanoacrylates, epoxy, isocyanates and the like. Fluid adhesives mayfurther include hot-melt adhesives, for example, pressure-sensitiveadhesives. Pressure-sensitive adhesives may include, but are not limitedto, tackified rubber adhesives, such as natural rubber, olefins,silicones, polyisoprene, polybutadiene, polyurethanes,styrene-isoprene-styrene and styrene-butadiene-styrene block copolymers,and other elastomers; and tackified or untackified acrylic adhesivessuch as copolymers of isooctylacrylate and acrylic acid, which can bepolymerized by radiation, solution, suspension, or emulsion techniques.As used herein, the phrase “solvent-based adhesive” refers to anadhesive system which comprises an adhesive and at least one solvent andrequires that the solvent be removed by evaporation (drying) after thesolvent-based adhesive is applied to at least one film substrate, layerand the like. A solvent-based adhesive may include a solvent such asconventional petrochemical-based solvents, i.e., for example, but notlimited to, alcohols, toluene, esters, and the like, a water-basedsolvent, and combinations thereof. As used herein, the phrase“solvent-free adhesive” refers to an adhesive system which comprises anadhesive and may include a solvent, but does not require that thesolvent be removed by evaporation after the solvent-free adhesive isapplied to a film substrate, layer and the like. A solvent-free adhesivemay also comprise a solvent-free adhesive which is diluted with aconventional petrochemical-based or water-based solvent prior to coatingin order to facilitate its application. Solvent-free adhesives mayfurther comprise radiation-curable adhesives which polymerize and/orcross-link when exposed to ultraviolet light or ionizing radiationsources. Useful types of ionizing radiation sources include electronbeam (e-beam), X-ray, corona discharge, and the like, with the formerbeing preferred. Suitable radiation-curable adhesives are well knownsuch as those described in, for example, U.S. Pat. Nos. 4,256,828;4,593,051; 5,328,940; 6,617,031; 6,472,056; and U.S. Patent ApplicationPublication No. 2003/0161976, which are incorporated herein byreference.

As used herein, the term “gas-permeable” refers to any film or filmlayer having an oxygen transmission rate therethrough of greater than 5,10, 20, 50, 100, 500, 1,000 or 10,000 cm³/100 in²24 hours measured at 0%relative humidity and 23 degrees C.

As used herein, the phrases “sealing layer” and “sealant layer,” referto a film or an outer film layer involved in the sealing of a laminateto itself; to another laminate or film layer; and/or to a container. Ingeneral, the sealing layer is an interior surface and may be of anythickness. The interior surface may also serve as a product-contactsurface. In certain embodiments, the sealing layer may be a heat sealinglayer. In other embodiments, the sealing layer may be any suitableadhesive material.

The term “heat sealing layer” refers to a sealing layer which is heatsealable (i.e., capable of fusion bonding by conventional indirectheating means which generate sufficient heat on at least one filmcontact surface for conduction to the contiguous film contact surfaceand formation of a bond interface therebetween without loss of the layerintegrity). The bond interface between contiguous inner layerspreferably has sufficient physical strength to withstand the packagingprocess and subsequent handling including, for example, tensionsresulting from stretching or shrinking attendant with the presence of afood body sealed within a package utilizing a film having a heatsealable layer. Advantageously, the bond interface is preferablysufficiently thermally stable to prevent gas or liquid leakagetherethrough when exposed to above or below ambient temperatures, suchas those during one or more of the following: packaging operations,storage, handling, transport, display or processing of food. Heat sealsmay be designed to meet different conditions of expected use and variousheat seal formulations are known in the art and may be employed with thepresent disclosure. In certain optional embodiments, heat seals may besubjected to pasteurization or cook-in temperatures and conditions, forexample, in sealed bag, vacuum skin package (VSP) or sealed tray form.For use in cook-in applications, heat seals should withstand elevatedtemperatures up to about 160-180° F. (71-82° C.) or higher, for example,212° F. (100° C.) for extended periods of time, such as up to 4 to 12hours in environments which may range from heated humidified air orsteam to submersion in heated water Preferably, the sealing layer isheat sealable to itself, but may be sealable to other objects, films orlayers, such as to a tray when used as a lidding film or to an outerlayer in a lap seal or in certain tray overwrap embodiments. In otherembodiments, the heat sealing layer or the heat sealing layer andadjacent interior layers may be adapted to be peelable from itself orother objects. Also, in certain embodiments, the heat sealing layer mayalso serve as a product-contact layer.

By the term “substantially horizontal” it is meant that the majority ofa film surface is substantially parallel to a plane defined between twoopposing edges of a distal flange of a package.

Although specific embodiments of the present invention will now bedescribed with reference to the drawings, it should be understood thatsuch embodiments are by way of example only and merely illustrative ofbut a small number of the many possible specific embodiments which canrepresent applications of the principles of the present invention.

FIG. 1 depicts a partial cross-sectional diagram of one embodiment oflaminate 10 in accordance with the present invention. Laminate 10 isshown comprising a first film 11 having a first surface 11 a and anopposing second surface 11 b; a second film 12 having a first surface 12a and an opposing second surface 12 b; an adhesive 13; and anadhesive-free interfacial section 14. Second film 12 may include asealing layer (not shown). When the second film 12 has a monolayerstructure, the second film 12 serves as the sealing layer. In otherembodiments, one or both films 11 and 12, may have a multi-layerstructure and comprise a thermoplastic material, a non-thermoplasticmaterial or a combination of thermoplastic and non-thermoplasticmaterials. When second film 12 has a monolayer structure, second film 12comprises a thermoplastic material. Suitable thermoplastic materials foruse in the present invention may comprise any natural and syntheticplastic, which may include, for example, but is not limited to,homopolymers and copolymers of the following resins: polyolefins, suchas, low density polyethylenes, i.e., ultra- and very-low densitypolyethylene, linear-low density polyethylene, homogeneous andheterogeneous catalyzed low density polyethylenes, medium and highdensity polyethylenes, cyclic olefin copolymers, ethylene vinyl acetatecopolymers, polypropylene, polybutylene; polyamides, polyesters, forexample, polyethylene terephthalates; ionomers; natural and syntheticrubbers; polycarbonates; and derivates and combinations of thesematerials. Thermoplastic materials may include fibrous or non-fibrousnatural and synthetic plastics. Non-thermoplastic materials may include,but are not limited to, any fibrous or non-fibrous cellulosic material,such as, for example, paper and paperboard.

In accordance with the present invention, first film 11 and second film12 may each include specific materials which provide one or moreparticular package or film properties depending upon the manufacturingprocess used to produce the film and the final package end-use. Theseproperties may include package strength, film peel strength forpeelability, product damage protection, openability, reclosability,recycleability, and moisture, aroma, contaminant protection. Forexample, laminate 10 of the present invention may be adapted to packageoxygen-sensitive food and non-food products by providing the second film12 with one or more oxygen barrier materials. Alternatively, both firstfilm 11 and second film 12 may each comprise one or more oxygen barriermaterials. Oxygen barrier materials may be provided as a discrete layerand in combination with non-oxygen barrier materials. Suitable oxygenbarrier material may include, but are not limited to, thermoplasticresins such as nylons, ethylene vinyl alcohol copolymers, polyesters,metal and metal oxide coated polymer layers and combinations thereof.When an oxygen barrier material is present in a layer, the layer mayhave an oxygen transmission rate of less than 50 cm³/100 in²/24 hours,preferably, less than 20 cm³/100 in²/24 hours, and most preferably,between 0 to 5 cm³/100 in²/24 hours measured at 0% relative humidity and23 degrees C.

As shown in FIG. 1, adhesive 13 is disposed between first and secondfilms, 11 and 12, and preferably, bonds the second surface of first film11 b to the first surface of second film 12 a. Adhesive 13 may be clearor transparent, or it may be colored, and may be applied in liquid,semi-solid or solid form to the surface of either one or both filmsprior to lamination. Alternatively, adhesive 13 may be applied to thesurface of one or more films in a predetermined pattern. In oneembodiment, adhesive 13 is applied to the surface of either film 11 or12, such that less than 100%, less than 75%, less than 50%, or less than25% of the total area of the film surface is covered by the adhesive. Insome embodiments, it may be desirable to apply the adhesive as acontinuous or intermittent pattern on the surface of one or more films.For example, FIG. 5 illustrates one embodiment of the laminate accordingto the present invention with adhesive 13 applied to a surface of secondfilm 12 as two continuous adhesive segments, 13 a and 13 a′.Alternatively, FIG. 6 shows adhesive 13 disposed onto a surface ofsecond film 12 as one continuous segment of adhesive 13 b. FIG. 7further illustrates embodiment of the invention with adhesive 13 appliedto a surface of second film 12 as a plurality of intermittent adhesivesegments 13 c. It is further contemplated that adhesive 13 may beapplied to the surface of one or more films in any thickness, width orshape as desired. An example of a suitable adhesive for use in thepresent invention is Avadyne® AV5210/CA500-83 which may be purchasedfrom Henkel KGaA, Dusseldorf, Germany. The Avadyne AV5210/CA500-83system is identified as two-component ethanol-based adhesive having anamine-terminated polyurethane pre-polymer and a epoxy-terminated etherco-reactant.

Returning to FIG. 1, adhesive-free interfacial section 14 is positionedbetween first film 11 and second film 12. Adhesive-free interfacialsection 14 includes an unbound portion of the first film 15 and anunbound portion of the second film 16. In one preferred embodiment, atleast 50% of the total area of each film, 11 and 12, may be encompassedwithin unbound portion of the first film 15 and unbound portion of thesecond film 16, respectively. In another embodiment, unbound portion ofthe first film 15 is a thermoformable film and unbound portion of thesecond film 16 is a non-thermoformable film. It should be noted thatunbound portion of the first film 15 comprises at least one perforation,cut or score-line extending through the entire thickness of first film11. Preferably, unbound portion of the first film 15 is gas-permeable.As depicted in FIG. 1, unbound portion of the first film 15 includes aplurality of perforations, cuts and score-lines 17. Other variations ofperforations, cuts and score-lines which may be suitable for use inaccordance with the present invention and are illustrated in FIGS. 3 and4. In some preferred embodiments, the perforations, cuts and score-linesmay be formed in a predetermined pattern in unbound portion of the firstfilm 15. Preferably, the unbound portion of the second film 16 is freeof any perforations, cuts or score-lines. It should be appreciated bythose skilled in the art that any method may be used to form theperforation, cut or score-line in the first layer. These methods aregenerally well known and may include mechanical methods using a studdedrollers or knives, and optical techniques such as laser beam ablationand the like.

Turning now to FIG. 2, there is illustrated another embodiment of thepackaging laminate according to the present invention. As depicted,laminate 20 comprises a multilayer first film 21 which includes layers21 a and 21 b, a multilayer second film 22 which includes layers 22 aand 22 b. Laminate 20 also includes an adhesive 23 and an adhesive-freeinterfacial section 24. As shown, adhesive-free interfacial section 24includes an unbound portion of the first film 25 and an unbound portionof the second film 26. Unbound portion of the first film 25 comprises aplurality of perforations 27 that extend through the entire thickness offirst film 21. In this particular embodiment, second layer 22 b ofsecond film 22 may function as a sealing layer, preferably, a heatsealing layer.

The length and width of the films 11 and 21 may or may not becoextensive with those of the second films 12 and 22, respectively. Inone preferred embodiment, films 11 and 21 are coextensive with secondfilms 12 and 22, respectively. The first and second laminates 10 and 20in FIGS. 1 and 2 may each have any thickness desired, and preferably hasa thickness of between about 0.25 to 20 mil and more preferably, betweenabout 0.5 to 10 mil.

Depicted in FIG. 8 is flexible laminate 30 which is another preferredembodiment of a laminate according to the present invention. Asillustrated, laminate 30 comprises a monolayer first film 31, anadhesive 40, a multilayer second film 50, and an adhesive-freeinterfacial section 60. Adhesive-free interfacial section 60 includes anunbound portion of the first film 65 and an unbound portion of thesecond film 66. First film 31 is a thermoplastic film of orientedpolyethylene terephthalate having a thickness of 1.42 mil (142 gauge)which includes a plurality of perforations, 35 applied in apredetermined pattern therethrough. An example of a suitable orientedpolyethylene terephthalate which is commercially available is sold underthe trademark Mylar® by DuPont Teijin Films, Hopewell, Va., U.S.A. Aparticularly suitable example is Mylar® KLI having a haze value of 0.6%,an elongation at Break in the machine and transverse directions of 120%and 80%, respectively, and a tensile strength in the machine andtransverse directions of 33,000 psi and 38,000 psi, respectively. Asdepicted, second film 50 is a multilayer thermoplastic film comprisingseven individual layers, 51 through 57. Layer 51 comprises 91.7% (wt) ofa low-density polyethylene having a density of 0.920 g/cm³, a melt indexof 1.9 g/10 minutes, a melting point of 110′ C., which is identified asLD 134.09 and is available from ExxonMobil Chemical Company, Houston,Tex., United States, and 8.3% (wt) of a mixture of various film andpolymer additives. An example of another commercially availablelow-density polyethylene suitable for use in the present inventionincludes, but is not limited to, a polyethylene having a density of0.923 g/cm³, a melt index of 2.6 g/10 minutes, a melting point of 113°C., a Vicat softening point of 97° C., which is sold as Dow™Polyethylene 608A from the Dow Chemical Company, Midland, Mich., UnitedStates. Layers 52 and 56 each include 100% (wt) of an ionomer resinhaving a melt index of 1.5 g/10 minutes, a Vicat softening point of 73°C., a melting point of 97° C., which is sold under the trademark DuPont™Surlyn® 1650 and is available from du Pont de Nemours and Company, Inc.,Wilmington, Del., United States. Layers 53 and 55 are each a blend ofabout 75% (wt) of an ethylene/vinyl acetate copolymer having a densityof 0.93 g/cm³, a melt index of 0.35 g/10 minutes, a melting point of 95°C., a Vicat softening point of 82° C., which is sold under the trademarkDuPont™ Elvax® 3135XZ from du Pont de Nemours and Company, Inc.,Wilmington, Del.; and 25% (wt) of an anhydride-modified linearlow-density polyethylene having a melt index of 2.7 g/10 minutes, aVicat softening point of 103° C., a melting point of 115° C. and adensity of 0.91 g/cm³, which is sold under the trademark DuPont™ Bynel®41E710 and is also available from du Pont de Nemours and Company, Inc.,Wilmington, Del., United States. Layer 54 comprises an oxygen barriermaterial of ethylene/vinyl alcohol copolymer having an ethylene contentof 38% (wt.), a density of 1.17 g/cm³, a melt index of 3.2 g/10 minutes,a melting point of 173° C., a glass transition temperature of 58° C.,and sold under the trademark Soarnol® ET3803 which is available fromSoarus L.L.C., Arlington Heights, Ill., United States. Layer 57comprises 96% (wt) of an ethylene/vinyl acetate copolymer having adensity of 0.93 g/cm³, a melt index of 0.35 g/10 minutes, a meltingpoint of 95° C., a Vicat softening point of 82° C., which is sold underthe trademark DuPont™ Elvax® 3135XZ from du Pont de Nemours and Company,Inc., Wilmington, Del.; and 4% (wt) of a mixture of various additives.Layer 57 serves as a scaling layer, preferably, a heat scaling layer.The total thickness of the second film 50 is approximately 6 mil.

Film 50 may be produced using simple blown film processes which aredescribed, for example, in The Encyclopedia of Chemical Technology,Kirk-Othmer, Third Edition, John Wiley & Sons, New York, 1981, Vol. 16,pp. 416-417 and Vol. 18, pp. 191-192, the disclosures of which areincorporated herein by reference. Generally, the simple blown filmprocess may include an apparatus having a multi-manifold circular diehead through which the film layers are forced and formed into acylindrical multilayer film bubble. The bubble may be quenched, e.g.,via cooled water bath, solid surface and/or air, and then ultimatelycollapsed and formed into a multilayer film. It is appreciated by aperson of ordinary skill in the art that cast extrusion techniques mayalso be used to fabricate the thermoplastic layer structures of thepresent invention.

Unless otherwise noted, the polymer resins utilized in the presentinvention are generally commercially available in pellet form and, asgenerally recognized in the art, may be melt blended or mechanicallymixed by well-known methods using commercially available equipmentincluding tumblers, mixers or blenders. Also, if desired, well-knownadditives such as processing aids, slip agents, anti-blocking agents andpigments, and mixtures thereof may be incorporated into the polymerlayers, by blending prior to extrusion. The resins and any additives maybe introduced to an extruder where the resins are melt-plastified byheating and then transferred to an extrusion (or coextrusion) die forformation into a tube. Extruder and die temperatures will generallydepend upon the particular resin or resin containing mixtures beingprocessed and suitable temperature ranges for commercially availableresins are generally known in the art, or are provided in technicalbulletins made available by resin manufacturers. Processing temperaturesmay vary depending upon other processing parameters chosen.

In the practice of this invention, it may be desirable to surface-treatthe exterior surface of a film or a film layer. The terms“surface-treat” and “surface-treatment” both refer to any techniquewhich alters the surface energy (or surface tension) of a film layer andmay include techniques such as, but is not limited to, corona, flame,and plasma treatment, ozone, ultra-high frequency electrical discharge,UV or laser bombardment, chemical priming, and the like. The phrase“corona treatment” refers to, in general, the process wherein anelectrical discharge generated by a high-voltage electric field passesthrough a polymer substrate. It is believed that the electricaldischarge or “corona” may ionize the oxygen molecules surrounding thesubstrate which chemically interact with the surface atoms of thesubstrate thereby changing the surface energy of the polymer substrate.

It may also be desirable to irradiate the laminate, a film, film layer,to cause crosslinking of at least one or more thermoplastic layers toimprove the abuse and/or puncture resistance and other physicalcharacteristics of the laminate. Crosslinking is the predominantreaction which occurs on irradiation of many polymers and results in theformation of carbon-carbon bonds between polymer chains. Crosslinkingmay be accomplished, for example, by irradiation using high energyelectrons, gamma-rays, beta particles and the like. The irradiationsource can be any electron beam generator operating in a range of about150-6000 kilovolts (6 megavolts) with a power output capable ofsupplying the desired dosage. The voltage can be adjusted to appropriatelevels which may be for example 1-6 million volts or higher or lower.Many apparatus for irradiating thermoplastic films are known to thoseskilled in the art. The most preferred amount of radiation is dependentupon the layer and its end use. One method for determining the degree of“cross-linking” or the amount of radiation absorbed by a material is tomeasure the “gel content.” As used herein, the term “gel content” refersto the relative extent of cross-linking within a polymeric material. Gelcontent is expressed as a relative percent (by weight) of the polymerhaving formed insoluble carbon-carbon bonds between polymers and may bedetermined by ASTM D-2765-01 Test Method, which is incorporated hereinby reference in its entirety.

It is noted that various combinations of layers and materials can beused in the formation of the first and second films, 31 and 50.Accordingly, both films according to the present invention may includeany number of layers as so desired.

The fabrication of the laminates of this invention can be accomplishedby using any of a number of known methods (e.g., extrusion coating,extrusion lamination, adhesive lamination, tape application). Prior tolamination, the first film may undergo a perforation process,preferably, to create perforations in a predetermined pattern. Thepatterned perforation may extend along the entire length of the film. Anadhesive material is to be used to bond the first and second filmstogether and may be coated onto the surface of one or both films,preferably, in a predetermined pattern. If, as is preferred, an adhesiveis applied solely to the first film, the film may have alternatingpatterns of adhesive and perforations. The alternating patterns mayextend along the length of the first film. Depending on the type ofadhesive used, a further step of drying or curing of the adhesive may berequired after its application. With an adhesive positioned between andin contact with both the first and second films, the films are pressedtogether, with or without heat, to form the assembled laminate. Thesteps of contacting and pressing the films together may be accomplishedsequentially or simultaneously. The final laminate is then wound arounda roller for storage or further processing.

Now turning to FIG. 9, there is illustrated one embodiment of a packageaccording to the present invention. As depicted, package 100 includes aproduct-support member 150 having an elevated distal flange 153, and aproduct 160. The product 160 is positioned on the product-support member150, preferably, with the top of the product being below the top offlange 153. Product-support member 150 may include a rigid or semi-rigidtray that may be formed from mono-layered or multilayered, andthermoformable or non-thermoplastic materials. Rigid and semirigidnon-thermoplastic materials may include, but are not limited to,thermosetting plastics, paper, paperboard and cardboard, and formablemetals such as metallic foils, e.g., aluminum foil. Rigid and semirigidthermoplastic materials may be used to produce the product-supportmember 150 by such thermoforming techniques as generally recognized inthe art which may include vacuum forming, pressure forming, plug assistor mechanical forming processes. In this embodiment, product-supportmember 150 is a semirigid or rigid thermoplastic tray. In manyinstances, the product-support member 150 may include an oxygen barriermaterial to protect an oxygen-sensitive product from oxygen gasexposure. Examples of such semi-rigid and rigid thermoplastic trays aredisclosed by Lischefski et al., in co-pending U.S. patent applicationSer. No. 11/416,966 entitled “Rigid and Semirigid Packaging Articles,”which is incorporated herein by reference. Package 100 also includeslaminate 101 having a perimeter edge 105 sealed to the distal flange153. In a preferred embodiment of the invention, at least two opposingperimeter edges 105 a and 105 b of laminate 101 are heat-sealed todistal flange 153. Laminate 101 comprises a first flexible film 111, asecond flexible film 112 adhesively joined to the first film 111, and anadhesive-free interfacial section 140. As depicted, adhesive-freeinterfacial section 140 includes an unbound portion of the first film145 and an unbound portion of the second film 146. In one embodiment,unbound portion of the first film 145 and unbound portion of the secondfilm 146 each include at least 50% of the total area of film 111 and112, respectively. Non-limiting examples of suitable laminates for usein package 100 may include laminates 10, 20 and 30 (as shown in FIGS. 1,2 and 8, respectively), as described hereinabove. As illustrated in FIG.9, second flexible film 112 is positioned between the first film 111 andproduct-support member 150. Package 100 further comprises asubstantially horizontal film-surface 170 positioned over product 160which comprises the unbound portion of the first film 145. Thesubstantially horizontal film-surface 170 is parallel to a plane (notshown) defined between the two opposing perimeter edges 105 a and 105 bof distal flange 153. Package 100 still further comprises a thermoformedsecond film-surface 180 which is conformed to the exterior shape ofproduct 160 and includes unbound portion of the second film 146. Asshown in FIG. 9, this particular embodiment of the invention includes aplurality of perforations 117 in substantially horizontal film-surface170 which extend through the entire thickness of the first film 111.

FIGS. 10 through 12 represent a preferred embodiment of a method offorming a package, in part, according to the present invention. During atypical vacuum skin packaging process, laminate 101 and product-supportmember 150 are subjected to heat and/or differential air pressure, i.e.,evacuation and pressurization. As shown in FIG. 10, the force ofevacuating the space between laminate 101 and product-support member 150cause laminate 101 to push or pull towards product-support member 150until laminate 101 is in contact with distal flange 153. At thepressurization stage in the process, the unbound portions of the firstand second films, 145 and 146, will separate from each other as depictedin FIG. 11. In FIG. 12, unbound portion of the second film 146 may thenbe drawn further towards product 160 and, subsequently conform aroundthe exterior shape of product 160. In this final stage, laminate 101seals to product-support member 150 by heat-fusion of the exteriorsurface of laminate 101 to distal flange 153. The steps of sealing oflaminate 101 to product-support member 150 and of forming unboundportion of the second film 146 around the exterior shape of product 160may be accomplished as two sequential steps or simultaneously as one.Preferably, the sealing of laminate 101 includes forming heat-seals toat least two opposing perimeter edges 105 a and 105 b of laminate 101.When the vacuum skin packaging process is completed, package 100provides a substantially horizontal first film-surface 170 disposedabove product 160 and a thermoformed second film-surface 180 enclosingproduct 160. Printed indicia previously applied to laminate 101 or alabel subsequently applied thereto may be located on the substantiallyhorizontal first film-surface 170 for maximum visibility to theconsumer.

It will be apparent to those skilled in the art that modifications andadditions can be made to the various embodiments described above,without departing from the true scope and spirit of the presentinvention. It should be understood that this invention is not intendedto be unduly limited by the illustrative embodiments set forth hereinand that such embodiments are presented by way of example only with thescope of the invention intended to be limited only by the claims setforth herein as follows.

1. A method for packaging a product, comprising the steps of: (a)providing a product-support member having an elevated distal flange; (b)positioning the product on the product-support member; (c) providing asingle flexible laminate comprising a first film being adhesively joinedto a second film, and having an adhesive-free interfacial sectionbetween the first and second films, wherein the adhesive-freeinterfacial section comprises an unbound portion of the first film andan unbound portion of the second film, (d) heating the laminate; (e)evacuating the space between both the laminate and product-supportmember, and subsequently pressurizing the space between both thelaminate and product-support member to separate the unbound portion ofthe first film from the unbound portion of the second film; (f)conforming a film-surface of the unbound portion of the second filmaround the exterior shape of the product; and (g) sealing at least twoopposing perimeter edges of the laminate to the distal flange therebyproviding a substantially horizontal film-surface disposed above theproduct.
 2. The method set forth in claim 1 wherein the substantiallyhorizontal film-surface comprises the unbound portion of the first film.3. The method set forth in claim 1 further comprising the step ofplacing a printed label on the unbound portion of the first film orprinting indicia on a surface of unbound portion of the first film. 4.The method set forth in claim 1 wherein the unbound portion of the firstfilm comprises at least one perforation, cut or score-line, extendingthrough the entire thickness of the first film, and the unbound portionof the second film is free of perforations, cuts and score lines.
 5. Themethod set forth in claim 1 wherein the second film comprises amultilayer thermoplastic film.
 6. The method set forth in claim 1wherein the product comprises a fresh meat product.